Make https://get.haskellstack.org/ work on Travis/Windows

[ndmitchell]

Using Travis, you can write a .travis.yml which targets Windows. That has enough to run curl and sh. However, the script at get.ehaskellstack.org doesn't have branches for Windows. I think if they were added it should work.

[borsboom]

Oh, interesting. We actually don't recommend using the get.haskellstack.org script to install Stack on CI systems, since we make no guarantees about its stability and you may end up with a newer version of stack that breaks your build when you're not expecting it.

But in principle, nothing against updating the script to support Windows when running in a bash environment.

[ndmitchell]

I wrote a version that does work on Windows through Travis, https://github.com/ndmitchell/travis-check/blob/master/install-stack.sh, and a test at https://travis-ci.org/ndmitchell/travis-check/jobs/483804082#L48. Any chance of that being lifted into the main script? It's probably not going to work anywhere but on Travis - but the old one didn't work there - so it's strictly improving.

I know you don't recommend using it on CI, and I know you recommend testing a pinned version, and recommend LTS. I disagree with all of those recommendations 😄

[borsboom]

I had a look at the script, and overall looks OK, but couple of questions:

1. Does it fail somewhat gracefully (with a useful error) if you're trying it in a Windows environment that isn't supported? E.g. what does it do if it can't find 7z.

2. It appears to install to /bin; is that the right place in this environment? No support for e.g. /usr/local/bin? It also doesn't appear to use the -d DESTDIR argument.

Can you make a PR with your changes?

[ndmitchell]

1. I don't have any idea. I'll try and get it slightly working or erroring well in those situations.
2. On Travis, only /bin and /usr/bin are on $PATH. As a result, I'd have to have a different default -d depending on which OS you were using. Or is there a nicer way around?

Will PR against etc/scripts/get-stack.sh one we figure out what it should do around 2.

[borsboom]

I do think supporting -d would be good, and it seems reasonable to have a different default -d depending on the OS. I have no idea what the best practice is for installing binaries on the PATH on Windows sh environments, so I'll leave the default to your discretion (/bin is fine with me).

[ndmitchell]

Thanks, raised a PR #4555. As a bonus, I made it work on Travis, Appveyor and Azure Pipelines.

[borsboom]

#4555 merged.

[ndmitchell]

Thanks! Any chance of deploying the updated script to the https://get.haskellstack.org now? It means I could simplify my CI scripts. @borsboom

[borsboom]

I've cherry-picked the changes into the stable branch. It should automatically propagate to https://get.haskellstack.org soon (let me know if it doesn't).